Seat belt restraint systems for automobiles often include a pretensioner which is structured to apply tension to the seat belt when an accident situation or a potential accident situation is detected. When the pretensioner is activated, the pretensioner eliminates any slack in the seat belt, and thus controls the physical space between the occupant and the seat belt. In this manner, the occupant of the seat is pulled tightly into the seat before a situation arises in which the occupant moves forwardly relative to the seat, thereby controllably restraining the occupant, reducing occupant excursion, and preventing undue loads when the occupant moves forwardly into the seat belt.
A retractor is another standard component of a seat belt restraint system which includes a spindle receiving the webbing material of the seat belt. The spindle is used to wind up and store the webbing. Generally, the spindle is locked in place upon detection at a potential accident situation in order to restrain the occupant via the seat belt. Recently, retractors have been designed having one or more force limiting elements which are structured to allow the spindle to rotate and pay out the webbing material of the seat belt upon reaching predetermined force levels between the occupant and seat belt. In this manner, the restraint force imposed on the occupant can be limited in a controlled manner, thereby providing a certain load limitation characteristics.
Despite these and other improvements to automobile restraint systems, there remains a need to provide a restraint system which is adaptive to differently sized occupants, and in particular which is capable of adapting both the pretentioning and the load limitation characteristics of the restraint system to the occupant.